The present invention relates to a hybrid compressor mainly used for vehicle air-conditioning systems. More specifically, the present invention pertains to a hybrid compressor that is driven by a plurality of drive sources. The drive sources include an engine and an electric motor.
Generally, a vehicle air-conditioning system includes a refrigeration circuit, which includes a compressor and an external circuit connected to the compressor. When the compressor is driven by the engine, refrigerant circulates in the refrigeration circuit and cools the passenger compartment. Typically, the compressor is connected to a single drive source, or the vehicle's engine, through an electromagnetic clutch. When the cooling capacity of the refrigeration circuit becomes excessive as the thermal load on the refrigeration circuit decreases, the electromagnetic clutch is turned off and the operation of the compressor is temporarily stopped. When the engine is stopped, the compressor is not operated and the cooling function is stopped whether the electromagnetic clutch is turned on or off.
Japanese Unexamined Utility Model Publication No. 6-87678 describes a hybrid compressor that is driven by an engine and an electric motor. When the engine is stopped, the compressor can be driven by the motor to cool the passenger compartment.
The hybrid compressor includes a compression mechanism having a drive shaft, an electric motor, and an electromagnetic clutch. The electric motor has an output shaft joined to the drive shaft, and the clutch is connected to the output shaft. The engine is connected to the output shaft through the clutch. When the clutch is turned on, engine power is transmitted to the drive shaft through the output shaft, which operates the compressor. In this state, the output shaft of the motor rotates with the drive shaft of the compressor. The rotation of the output shaft generates electromotive force in the motor, and electric power based on the electromotive force is used to charge a battery. When the engine is stopped, the clutch is turned off and the output shaft (drive shaft) is disconnected from the engine, the motor, which is powered by the battery, drives the compressor.
In the hybrid compressor of the Japanese publication, the clutch and the motor are both attached to the front end of the compression mechanism. In detail, the motor is attached to the front end of the compression mechanism, and a pulley is provided to surround the electric motor. Power of the engine is transmitted to the pulley. The clutch is located between the pulley and the motor. This increases the size of the mechanism, which includes the motor, the pulley, and the clutch. The load of this large mechanism is applied to one end of the drive shaft of the compression mechanism. Since the drive shaft is supported by bearings, the unbalanced nature of the load applied to the bearings wears the bearings, which hinders smooth rotation of the drive shaft. As a result, noise is produced during operation.
In another prior art compressor, the electromagnetic clutch is attached to the front end of the compressor mechanism, and the electric motor is located on the front end of the clutch mechanism. In other words, the clutch is between the motor and the compression mechanism. However, in this case, the compression mechanism and the motor, which are independent, are respectively attached to a frame in the engine compartment. This complicates the installation of the compressor. Also, a large space is required to accommodate the compressor, since it has a large axial dimension.
An objective of the present invention is to provide a compact hybrid compressor that reduces the imbalance of the load applied to its drive shaft.
To achieve the above objective, the present invention provides a hybrid compressor that is selectively driven by an engine and a motor. A gas compression mechanism including a drive shaft. The compression mechanism has a first end and a second end The second end is opposite to the first end. The motor is fixed to the second end, and the motor has an output shaft connected to the drive shaft. A clutch is fixed to the first end of the compression mechanism. The clutch selectively transmits power from the engine to the drive shaft.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.